1. Field of the Invention
Aspects of the invention relate to technology that can control a sensing operation of a communication apparatus in a communication system using cognitive radio technology.
2. Description of the Related Art
According to cognitive radio technology, a communication apparatus belonging to a secondary system periodically or non-periodically senses frequency resources that are not used by a primary system, identifies an available frequency resource, and transmits and receives data using the available frequency resource. With respect to the available frequency resource, the primary system has priority over the secondary system. When there is a likelihood that a signal of the secondary system may conflict with a signal of the primary system, the communication apparatus of the secondary system must suspend a communication operation or change a frequency band in use.
Currently, research is being conducted regarding determining whether the secondary system is performing the communication operation. One scheme in particular that sequentially performs a fast sensing operation and a fine sensing operation is receiving much attention. According to the above scheme, the secondary system can quickly determine whether a signal received during a fast sensing section exists. The fast sensing section can be a relatively short time slot. The secondary system can compare power of the received signal with a predetermined sensing level to thereby quickly determine whether the received signal exists. If the signal received during the fast sensing section exists, the secondary system can specifically determine whether a signal received during a fine sensing section is transmitted from the primary system. The fine sensing section can be a relatively long time slot. The secondary system can specifically determine whether the received signal is transmitted from the primary system using a matched filter and the like.
There is a need to control a sensing operation of the secondary system. For example, when a channel being used by the primary system rarely changes, the secondary system should not frequently perform the sensing operation. Conversely, when the channel being used by the primary system changes frequently, the secondary system should perform the sensing operation frequently. Accordingly, there is a need for technology that can control a sensing operation of a secondary system according to a channel occupancy state of a primary system.